text: Given the Gauckler–Manning–Strickler formula:
  where:
   is velocity in meters per second, <br />
   is n-value in seconds per meter, <br />
   is the Strickler coefficient, , <br />
   is hydraulic radius in meters, and <br />
   is the dimensionless water surface slope.
  Substituting Strickler’s equation for n-value and rearranging terms produces a dimensionally homogeneous form of the Manning’s formula:
  Where  is acceleration due to gravity in meters per second.
  The first term on the right-hand side of the equation is the dimensionless ratio of hydraulic radius to roughness height,  commonly referred to as relative roughness. The remaining term, known as the boundary shear velocity, approximates the flow of water downhill under the influence of gravity and has units of velocity, i.e., L/T. 
  From experimental data, Stickler proposed that the dimensionally homogeneous form of the Manning formula could be quantified as:
  where 
  In civil engineering practice, the Manning formula is more widely used than Stricker’s dimensionally homogeneous form of the equation. However, Strickler’s observations on the influence of surface roughness and the concept of relative roughness are common features of a variety of formulas used to estimate hydraulic roughness.